Automatic focusing method, and automatic focusing device, image capturing device using the same

ABSTRACT

The present invention illustrates an automatic focusing method. Firstly, through multiple cameras of an image capturing device, a scene is captured, such that multiple images generated corresponding to the cameras are obtained. Then, multiple depth maps are generated according to the images. Next, according to the resolutions of single one or multiple objects in the depth maps, the depth information of the single one or multiple objects in the depth maps can be selected to generate a merged depth map. Then, a target focus distance of the single one object or target focus distances of multiple objects are calculated according to the merged depth map. Next, an actual focus distance of the multi-lenses module associated with the cameras is adjusted according to the target focus distance of the single one object or one of the multiple objects.

BACKGROUND

1. Technical Field

The present disclosure relates to an image capturing device; inparticular, to an automatic focusing method executed in the imagecapturing device which has a plurality of cameras, and an automaticfocusing device and the image capturing device which use the automaticfocusing method.

2. Description of Related Art

The current image capturing device is usually a digital image capturingdevice, which can automatically find a focus distance by using at leastone of the software, hardware, firmware, such that a photographer cantake a picture which has a clear scene. Referring to FIG. 1, FIG. 1 is acurve diagram showing a focusing evaluation value and a step movementindex after the conventional automatic focusing method executed in theimage capturing device with a single one lens module moves the lensmodule each time. The conventional automatic focusing method graduallymoves the lens module to adjust the focus distance of the lens moduleand obtain the corresponding focusing evaluation value, such as thecontrast or clarity of the image. The conventional automatic focusingmethod can find the focus distance corresponding to the maximum focusingevaluation value after gradually moving the lens module several times,and the focus distance corresponding to the maximum focusing evaluationvalue may be the correct focus distance.

In FIG. 1, during the procedure of the first seven lens modulemovements, the focusing evaluation value which is obtained after thelens module moves current time is larger than the focusing evaluationvalue which is obtained after the lens module moves previous time.However, the focusing evaluation value which is obtained after the lensmodule moves eighth time is less than the focusing evaluation valuewhich is obtained after the lens module moves seventh time. Theconventional automatic focusing method considers that the focus distancecorresponding to the seventh lens module movement may be the correctfocus distance corresponding to the scene currently captured by imagecapturing device, and thus sets the focus distance corresponding to theseventh lens module movement to the focus distance which the imagecapturing device can capture the scene currently, so as to finish theprocedures of the conventional automatic focusing method. It is notedthat, the automatic focusing method in the example must capture eightimages, and thus the speed for automatic focusing is not fast. Inaddition, since the conventional automatic focusing method must move thelens module several times, the movement deviation of the actuator isaccumulated during the automatic focusing procedure.

SUMMARY

An exemplary embodiment of the present disclosure provides an automaticfocusing method executed in an image capturing device. Through multiplecameras of the image capturing device, a scene is captured, so as toobtain multiple images generated corresponding to the cameras, whereinthe scene comprises a single one object or multiple objects. Multipledepth maps are generated according to the images, wherein each of thedepth map is generated according to the arbitrary two images, and thedepth map has depth information of the single one object or at least oneof the multiple objects, or does not have the depth information of thesingle one object or all of the multiple objects. According toresolutions of the single one or the multiple objects in the depth maps,the depth information of the single one or the multiple objects in thedepth maps is selected to generate a merged depth map. According to themerged depth map, a target focus distance of the single one object ortarget focus distances of the multiple objects are calculated. Accordingto the target focus distance of the single one object or one of thetarget focus distances of the multiple objects, an actual focus distanceof the multi-lenses module associated with the cameras is adjusted.

An exemplary embodiment of the present disclosure provides an automaticfocusing device adapted to an image capturing device, and the automaticfocusing device comprises a merged depth map generating module and afocus distance calculating module, wherein the merged depth mapgenerating module is electrically connected to the image capturingmodule, and the focus distance calculating module is electricallyconnected to the merged depth map generating module and the imagecapturing module. The merged depth map generating module and the focusdistance calculating module jointly execute portion of the steps in theautomatic focusing method.

An exemplary embodiment of the present disclosure provides an imagecapturing device comprising an image capturing module and the automaticfocusing device, wherein the image capturing module has multiplecameras, and comprises a multi-lenses module, a multi-sensors module,and an actuator module. The image capturing device executes each of thesteps in the automatic focusing method.

To sum up, the automatic focusing method, the automatic focusing deviceand the image capturing device using the method can automatically findthe actual focus distance fast and accurately.

In order to further understand the techniques, means and effects of thepresent disclosure, the following detailed descriptions and appendeddrawings are hereby referred, such that, through which, the purposes,features and aspects of the present disclosure can be thoroughly andconcretely appreciated; however, the appended drawings are merelyprovided for reference and illustration, without any intention to beused for limiting the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the present disclosure, and are incorporated in andconstitute a part of this specification. The drawings illustrateexemplary embodiments of the present disclosure and, together with thedescription, serve to explain the principles of the present disclosure.

FIG. 1 is a curve diagram showing a focusing evaluation value and a stepmovement index after the conventional automatic focusing method executedin the image capturing device with a single one lens module moves thelens module each time.

FIG. 2 is a schematic diagram showing an image capturing deviceaccording to an exemplary embodiment of the present disclosure.

FIG. 3 is a schematic diagram showing an image capturing moduleaccording to an exemplary embodiment of the present disclosure.

FIG. 4 is a schematic diagram showing an automatic focusing methodaccording to an exemplary embodiment of the present disclosure.

FIG. 5A is a schematic diagram showing the usage scenario of theautomatic focusing method for an actual scene according to an exemplaryembodiment of the present disclosure.

FIG. 5B is a schematic diagram showing the usage scenario of theautomatic focusing method for another actual scene according to anotherexemplary embodiment of the present disclosure.

DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

Reference will now be made in detail to the exemplary embodiments of thepresent disclosure, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same reference numbers areused in the drawings and the description to refer to the same or similarparts.

An exemplary embodiment of the present disclosure provides an automaticfocusing method adapted to an image capturing device with multiplecameras. The automatic focusing method captures a scene through thecameras to obtain multiple images corresponding to the cameras. Thescene can has single one object or multiple objects, and the object canbe a background, animal, landmark, human, tree, cloud, mountain, orwaterfall. Next, the automatic focusing method can generate multipledepth maps according to the images, wherein each depth map is generatedby the arbitrary two images. The depth map has depth information of thesingle one object or at least one of the multiple objects (if the twoimages which form the depth map have the single one object or at leastthe same one of multiple objects), or does not have the depthinformation of the single one object or all of the multiple objects (ifthe two images which form the depth map do not have the single oneobject or at least the same one of multiple objects).

Resolutions of the single one object or the multiple objects in thedepth maps are different from each other. According to the resolutionsof the single one object or the multiple objects in the depth maps, theautomatic focusing method selects depth information of the single oneobject or the multiple objects in the depth maps to generate a mergeddepth map.

Concretely, in one exemplary embodiment of the present disclosure, forthe single one object or each of the multiple objects, if the objectappears in portion or all of the depth maps, the automatic focusingmethod selects the depth information of the object in the depth mapwhich has a maximum resolution of the object as depth information of theobject in the merged depth map. For the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the automatic focusing method selects the depth information of theobject in the depth map as the depth information of the object in themerged depth map.

In addition, one of implementations for selecting the depth informationof the object in the depth map which has the maximum resolution of theobject as the depth information of the object in the merged depth map isdescribed as follows.

For the single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, the automatic focusingmethod compares the resolutions of the object in the depth maps, andselects the depth information of the object in the depth map which has amaximum resolution of the object as the depth information of the objectin the merged depth map. For the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the automatic focusing method selects the depth information of theobject in the depth map as the depth information of the object in themerged depth map.

Notably, the implementation for generating the merged depth map notlimited to the manner for selecting the depth information of the objectin the depth map which has a maximum resolution of the object as thedepth information of object in the merged depth map. The otherimplementations for generating the merged depth map are illustrated asfollows.

In another exemplary embodiment of the present disclosure, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the automatic focusing methodselects the depth information of the object in one of the depth mapswhich have the resolutions of the object larger than a thresholdresolution as depth information of the object in the merged depth map.For the single one object or each of the multiple objects, if the objectmerely appears in one of the depth maps, the automatic focusing methodselects the depth information of the object in the depth map as thedepth information of the object in the merged depth map.

In addition to the implementation for generating the merged depth map,another implementation for generating the merged depth map isillustrated as follows. In another exemplary embodiment of the presentdisclosure, for the single one object or each of the multiple objects,if the object appears in the portion or all of the depth maps, theautomatic focusing method performs a weighting calculation on the depthinformation of the object in the depth maps which have the resolutionsof the object larger than the threshold resolution, and selects weighteddepth information of the object as depth information of the object inthe merged depth map. For the single one object or each of the multipleobjects, if the object merely appears in one of the depth maps, theautomatic focusing method selects the depth information of the object inthe depth map as the depth information of the object in the merged depthmap.

In addition to the implementation for generating the merged depth map,another implementation for generating the merged depth map isillustrated as follows. In another exemplary embodiment of the presentdisclosure, for the single one object or each of the multiple objects,if the object appears in the portion or all of the depth maps, theautomatic focusing method performs the weighting calculation on thedepth information of the object in the depth maps which have theresolutions of the object within top ranks (for example, the top 60%,but the present disclosure is not limited thereto), and selects weighteddepth information of the object as depth information of the object inthe merged depth map. For the single one object or each of the multipleobjects, if the object merely appears in one of the depth maps, theautomatic focusing method selects the depth information of the object inthe depth map as the depth information of the object in the merged depthmap.

After the merged depth map is generated, the automatic focusing methodcalculates a target focus distance of the single one object or targetfocus distances of the multiple objects according to the merged depthmap. Next, the automatic focusing method adjusts an actual focusdistance of the multi-lenses module associated with the camerasaccording to the target focus distance of the single one object or oneof the target focus distances of the multiple objects (selected by theuser manually or the automatic focusing device automatically), whereinthe automatic focusing method can adjust the actual focus distance ofthe multi-lenses module once or step by step, and the present disclosureis not limited thereto.

In addition, an exemplary embodiment of the present disclosure providesan automatic focusing device adapted to an image capturing device havingmultiple cameras. The automatic focusing device has a merged depth mapgenerating module and a focus distance calculating module. The mergeddepth map generating module generates the merged depth map by using thementioned manner. The focus distance calculating module calculates thetarget focus distances by using the mentioned manner. In addition, theautomatic focusing device further comprises a control interface to allowthe user select one of the target focus distances of the multipleobjects, and to transmit the selected one of the target focus distancesof the multiple objects to the actuator module, such that the actuatormodule can adjust the actual focus distance of the multiple-lensesmodule associated with the cameras.

An exemplary embodiment of the present disclosure further provides animage capturing device using said automatic focusing method, wherein theimage capturing device has the image capturing module and the automaticfocusing device which have multiple cameras.

Accompanying with drawings, the automatic focusing method, module, andthe image capturing device are illustrated as follows. However, thefollowing exemplary embodiments are not intended to limit the presentdisclosure.

[Exemplary Embodiment of Image Capturing Device]

Referring to FIG. 2, FIG. 2 is a schematic diagram showing an imagecapturing device according to an exemplary embodiment of the presentdisclosure. The image capturing device 2 comprises an image capturingmodule 21 and an automatic focusing device 22, wherein the imagecapturing module 21 is electrically connected to the automatic focusingdevice 22.

The image capturing module 21 has multiple cameras, and the cameras canbe a camera array, which has multiple lenses and corresponding sensingunits arranged as an N×M array. One of the lenses corresponds to one ofthe sensing units. The distance between the two neighboring lenses onthe horizontal or vertical direction is L, and the distance between twoneighboring lenses on diagonal direction is √{square root over (2)}L.The image capturing module 21 captures a scene through the cameras toobtain multiple images corresponding to the cameras, wherein the scenecan have single one object or multiple objects.

In the exemplary embodiment, N and M are integers larger than or equalto 1, but a product of N and M are larger than or equal to 3. Forexample, M and N can be 4. Though the cameras in the exemplaryembodiment of FIG. 2 can be the camera array, the present disclosuredoes not limit the arrangement of the cameras, and the cameras is notlimited to be the camera array.

The automatic focusing device 22 receives the images, and generatesmultiple depth maps according to the images, wherein the depth map isgenerated from the arbitrary two images, and the depth map has depthinformation of the single one object or at least the same one of themultiple objects in the corresponding two images. The automatic focusingdevice 22 selects the depth information of the single one or themultiple objects in the depth maps to generate a merged depth mapaccording to resolutions of the single one or the multiple objects inthe depth maps. In other words, whether the depth information of thesingle one object or each of the multiple objects in the depth maps canbe selected to generate the merged depth map is determined based on theresolutions of the single one object or each of the multiple objects inthe depth maps. By the way, the resolution of the single one object oreach of the multiple objects is related to the distance of two lenses2111 associated with the two corresponding images of the depth map.

One implementation that the automatic focusing device generates themerged depth map is illustrated as follows. For the single one object oreach of the multiple objects, if the object appears in the portion orall of the depth maps, the automatic focusing device 22 finds the depthmap having a maximum resolution of the object, and selects the depthinformation of the object in the found depth map as the depthinformation of object in the merged depth map, that is, the depthinformation of the object in the depth map which has the maximumresolution of the object is selected to the merged depth map. For thesingle one object or each of the multiple objects, if the object merelyappears in one of the depth maps, the automatic focusing device 22directly selects the depth information of the object in the depth map asthe depth information of the object in the merged depth map.

Specifically, for the single one object or each of the multiple objects,if the object appears in portion or all of the depth maps, the automaticfocusing device 22 compares the resolutions of the object in the depthmaps, and selects the depth information of the object in the depth mapwhich has the maximum resolution of the object as the depth informationof the merged depth map. For the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the automatic focusing device 22 directly selects the depth informationof the object in the depth map as the depth information of the object inthe merged depth map.

It is noted that, the present disclosure does not limit to select thedepth information of the object in the depth map which has the maximumresolution of the object as the depth information of the merged depthmap. Another implementation for generating the merged depth map isillustrated as follows.

In another implementation for generating the merged depth map, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the automatic focusing device22 performs a weighting calculation on the depth information of theobject in the depth maps which have the resolutions of the object withintop ranks, and selects the weighted depth information of the object asthe depth information of the object in the merged depth map. For thesingle one object or each of the multiple objects, if the object merelyappears in one of the depth maps, the automatic focusing device 22directly selects the depth information of the object in the depth map asthe depth information of the object in the merged depth map.

In another implementation for generating the merged depth map, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the automatic focusing device22 compares the resolutions of the object in the depth maps with thethreshold resolution, and randomly selects the depth information of theobject in one of the depth maps which have the resolutions of the objectlarger than the threshold resolution as the depth information of theobject in the merged depth map. For the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the automatic focusing device 22 directly selects the depth informationof the object in the depth map as the depth information of the object inthe merged depth map.

In another implementation for generating the merged depth map, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the automatic focusing device22 performs the weighting calculation on the depth information of theobject in the depth maps which have the resolutions of the object largerthan the threshold resolution, and selects the weighted depthinformation of the object as the depth information of the object in themerged depth map. For the single one object or each of the multipleobjects, if the object merely appears in one of the depth maps, theautomatic focusing device 22 selects the depth information of the objectin the depth map as the depth information of the object in the mergeddepth map.

Next, the automatic focusing device 22 calculates a target focusdistance of the single one object or focus distances of the multipleobjects according to the depth information of the single one object orthe multiple objects in the merged depth map, and the target distance ofthe single one object or one of the multiple objects is transmitted toactuator module 213, such that the actuator module 213 can adjust anactual focus distance of the cameras associated with the multi-lensesmodule 211 (i.e. the actual focus distance of the lenses 2111) accordingto the target focus distance of the single one object or one of themultiple objects.

One implementation of the image capturing module 21 is illustrated asfollows, and the present disclosure is not limited thereto. The imagecapturing module 21 comprises a multi-lenses module 211, a multi-sensorsmodule 212, and an actuator module 213, wherein the multi-lenses module211 is connected to the actuator module 213, the actuator module 213 iselectrically connected to the automatic focusing device 22, and themulti-sensors module 212 is electrically to the automatic focusingdevice 22. The multi-lenses module 211 and the multi-sensors module 212form the cameras, and the cameras can be the camera array.

The multi-lenses module 211 has multiple lenses 2111 arranged as anarray, wherein the distance between the two neighboring lenses 2111 onthe horizontal or vertical direction is L, and the distance between thetwo neighboring lenses 2111 on the diagonal direction is √{square rootover (2)}L. The sensing units of the multi-sensors module 212 capturethe scene on the images by using the multi-lenses module 211.

Each of the sensing units associated with the multi-sensors module 212corresponds to one of the lenses 2111. In the exemplary embodiment, thesensing units of the multi-sensors module 212 can be arranged as an N×Marray (N rows and M columns), and the present disclosure does not limitthe arrangement of the sensing units. The multi-sensors module 212generates the images according to the light collected from the lenses2111. Each of the sensing units associated with the multi-sensors module212 further has a color filter module comprising a red, blue, greencolor filter for example, and the color filter module can further filterinfrared ray. Notably, the present disclosure does not limit the type ofthe color filter module.

The actuator module 213 receives the target focus distance of the singleone object or one of the multiple objects, which is calculated by theautomatic focusing device 22. The actuator module 213 adjusts the actualfocus distance of the multi-lenses module 211 associated with thecameras according to the received target focus distance, so that theactual focus distance of the multi-lenses module 211 can be equal to thereceived target focus distance.

The actuator module 213 in the exemplary embodiment can be a closed-loopactuator module, and the present disclosure is not limited thereto. Theactuator module 213 in other exemplary embodiment can be an open-loopactuator module. In FIG. 2, the actuator module 213 comprises anactuator driver 2131, an actuator 2132, a closed-loop controller 2133,and a location sensor 2134, wherein the actuator driver 2131 iselectrically connected to the automatic focusing device 22, the actuatordriver 2131 is electrically connected to the actuator 2132 and theclosed-loop controller 2133, the actuator 2132 is connected to themulti-lenses module 211, and the location sensor 2134 is electricallyconnected to the closed-loop controller 2133.

The actuator driver 2131 receives the feedback signal from theclosed-loop controller 2133 and the target focus distance of the singleone object or one of the multiple objects, which is calculated by theautomatic focusing device 22, so as to generate a driving signal to theactuator 2132 according to the feedback signal and the received targetfocus distance. The actuator 2132 receives the driving signal, andadjusts the actual focus distance of the multi-lenses module 211according to the driving signal. The location sensor 2134 senses theactual focus distance of the multi-lenses module 211, through directlysensing the location of the multi-lenses module 211 or the act of theactuator 2132 for example, and generates a location signal to theclosed-loop controller 2133. The closed-loop controller 2133 generatesthe feedback signal to actuator driver 2131 according to the locationsignal, such that the actuator module 213 can accurately adjust theactual focus distance of the multi-lenses module 211 to be the receivedtarget focus distance.

One implementation of the automatic focusing device 22 is illustrated asfollows, and the present disclosure does not limit the implementation ofthe automatic focusing device 22. The automatic focusing device 22 canbe implemented by at least one of the software, hardware, and firmware.The automatic focusing device 22 comprises a merged depth map generatingmodule 221, a focus distance calculating module 222, and a controlinterface 223, wherein the merged depth map generating module 221 iselectrically connected to the focus distance calculating module 222 andthe multi-sensors module 212 of image capturing module 21, and thecontrol interface 223 is electrically connected to the focus distancecalculating module 222 and the actuator module 213 of the imagecapturing module 21.

The merged depth map generating module 221 receives the imagescorresponding to the cameras, and generates the depth maps according tothe images, wherein the depth map is generated according to thearbitrary two images, and the depth map has depth information of thesingle one object or at least one of the multiple objects (if the twoimages which form the depth map have the single one object or at leastthe same one of multiple objects), or does not have the depthinformation of the single one object or all of the multiple objects (ifthe two images which form the depth map do not have the single oneobject or at least the same one of multiple objects). Next, the mergeddepth map generating module 221 selects the depth information of thesingle one or the multiple objects in the depth maps to generate amerged depth map according to resolutions of the single one or themultiple objects in the depth maps.

The focus distance calculating module 222 calculates a target focusdistance of the single one object or target focus distances of themultiple objects according to the merged depth map, wherein the targetfocus distance of the single one object or one of the target focusdistances of the multiple objects is used to adjust the actual focusdistance of the multi-lenses module 212 associated with the cameras. Thecontrol interface 223 allows the user to select the target focusdistance of the single one object or one of the target focus distancesof the multiple objects, or automatically selects the target focusdistance of the single one object or one of the target focus distancesof the multiple objects according to a system default selection command,and transmits the selected target focus distance of the object to theactuator module 213.

One implementation of the merged depth map generating module 221 isillustrated as follow, and the present disclosure does not limit theimplementation of the merged depth map generating module 221. The mergeddepth map generating module 221 comprises storage devices 2210, 2210′,2210″, a depth map generator 2211, a resolution comparator 2212, and adepth map merger 2213, wherein the storage device 2210 is electricallyconnected between the multi-sensors module 212 and the depth mapgenerator 2211, the storage device 2210′ is electrically connectedbetween the depth map generator 2211 and the resolution comparator 2212,the depth map merger 2213 is electrically connected between theresolution comparator 2212 and the storage device 2210″, and the storagedevice 2210″ is electrically connected to the focus distance calculatingmodule 222.

The storage device 2210 stores the images which the cameras capture thescene, the storage device 2210′ stores the depth maps, and the storagedevice 2210″ stores the merged depth map. The storage devices 2210,2210′, and 2210″ belong to the portion of the merged depth mapgenerating module 221 in the exemplary embodiment, but however can bethe external storage devices connected to the merged depth mapgenerating module 221 in one other exemplary embodiment. Furthermore,the storage devices 2210, 2210′, and 2210″ in the exemplary embodimentare three independent devices, but however the storage devices 2210,2210′, and 2210″ can be integrated into one storage device in one otherexemplary embodiment for storing the images, depth maps, and mergeddepth map. In short, the number and type of the storage devices 2210,2210′, and 2210″ are not used to limit the present disclosure.

The depth map generator 2211 receives the images corresponding to thecameras, and generates the depth maps according to the images, and thestorage device 2210′ stores the depth maps. Each depth map is generatedby the arbitrary two images. The depth map has depth information of thesingle one object or at least one of the multiple objects (if the twoimages which form the depth map have the single one object or at leastthe same one of multiple objects), or does not have the depthinformation of the single one object or all of the multiple objects (ifthe two images which form the depth map do not have the single oneobject or at least the same one of multiple objects). Specifically, ifthe two images have the single object or at least the same one of themultiple objects, the locations of the same object in the two images arenot the same one since the two images correspond to the different lensmodules 2111. By using the difference between the locations of the sameobject in the two images, the depth information of the object can beobtained, and depth map is thus generated accordingly.

One implementation for identifying whether the two images have the sameobject is illustrated as follows. The currently used object identifyingmethod, such as face identifying method or one other known objectidentifying method can be used to extract the objects in the two images,and then calculate the correlation of the objects of the two images todetermine whether the two images have the same object. However, thepresent disclosure does not limit the implementation for identifyingwhether the two images have the same object, and the person withordinary skill in the art may select one other implementation foridentifying whether the two images have the same object.

In one exemplary embodiment, for the single one object or each of themultiple objects, if the object appears in the portion or all of thedepth maps, the resolution comparator 2212 compares the resolutions ofthe object in the depth maps to find the depth map having the maximumresolution of the object. Then, the depth map merger 2213 determines andselects the depth information of the object in the depth map which hasthe maximum resolution of the object as the depth information of objectin the merged depth map according to the comparison result of theresolution comparator 2212. Thus, the depth information of the singleone object and each of the multiple objects in the merged depth map isthe depth information of the object in the depth map which has themaximum resolution of the object. For the single one object or each ofthe multiple objects, if the object merely appears in one of the depthmaps, the merged depth map generating module 221 directly selects thedepth information of the object in the depth map as the depthinformation of the object in the merged depth map.

For example, there are three depth maps generated, wherein both thefirst and second depth maps have the depth information of objects A andB, and the third depth map has the depth information of objects A, B,and C. Assuming the resolution of the object A in the first depth map islarger than those in the second and third depth maps, the depthinformation of the object A in the first depth map is selected to themerged depth map (i.e. the depth information of the object A in themerged depth map is the same as that in the first depth map) after theresolutions of the object A in the three depth maps are compared.Assuming the resolution of the object B in the second depth map islarger than those in the first and third depth maps, the depthinformation of the object B in the second depth map is selected to themerged depth map (i.e. the depth information of the object B in themerged depth map is the same as that in the second depth map) after theresolutions of the object B in the three depth maps are compared. Theresolutions of the object C in the three depth maps will not be comparedsince merely the third depth map has the object C, and the depthinformation of the object C is selected to the merged depth map (i.e.the depth information of the object C in the merged depth map is thesame as that in the third depth map).

As mentioned above, the present disclosure does not limit to select thedepth information of the object in the depth map which has a maximumresolution of the object as the depth information of object in themerged depth map.

In other implementation for generating the merged depth map, at the step“according to the resolutions of the single one or the multiple objectsin the depth maps, selecting the depth information of the single one orthe multiple objects in the depth maps to generate a merged depth map”,for the single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, the resolutioncomparator 2212 compares the resolutions of the object in the depthmaps, and the depth map merger 2213 performs the weighting calculationon the depth information of the object in the depth maps which have theresolutions of the object within the top ranks to select the weighteddepth information of the object as the depth information of the objectin the merged depth map. For the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth map merger 2213 directly selects the depth information of theobject in the depth map as the depth information of the object in themerged depth map.

In other implementation for generating the merged depth map, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the resolution comparator 2212compares the resolutions of the object in the depth maps with thethreshold resolution, and the depth map merger 2213 selects the depthinformation of the object in one of the depth maps which have theresolution of the object larger than the threshold resolution as thedepth information of the object in the merged depth map. For the singleone object or each of the multiple objects, if the object merely appearsin one of the depth maps, the depth map merger 2213 directly selects thedepth information of the object in the depth map as the depthinformation of the object in the merged depth map.

In other implementation for generating the merged depth map, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the resolution comparator 2212compares the resolutions of the object in the depth maps with thethreshold resolution, and the depth map merger 2213 performs theweighting calculation on the depth information of the object in thedepth maps which have the resolutions of the object larger than thethreshold resolution and selects the weighted depth information of theobject as the depth information of the object in the merged depth map.For the single one object or each of the multiple objects, if the objectmerely appears in one of the depth maps, the depth map merger 2213directly selects the depth information of the object in the depth map asthe depth information of the object in the merged depth map.

Take the implementation for performing the weighting calculation on thedepth information of the object in the depth maps which have resolutionsof the object within the top ranks and selecting the weighted depthinformation of the object as the depth information of the object in themerged depth map as the example. When the image capturing module 21 haveeight cameras, 28 (C₂ ⁸) images are generated accordingly. Assuming theobject A appears in the first, second, fourth, fifth, and ninth depthmaps, the object B appears in the 14^(th), 15^(th), 16^(th), 19^(th),and 20^(th) depth maps, the rank of the resolutions of the object A inthese depth maps is the second, fourth, ninth, fifth, and first depthmaps, and the rank of the resolutions of the object B in these depthmaps is the 20^(th), 16^(th), 19^(th), 15^(th), and 14^(th) depth maps,the depth map merger 2213 performs the weighting calculation on thedepth information of the object A in the second, fourth, and ninth depthmaps (the top 60% for example), and on the depth information of theobject B in the 20^(th), 16^(th), and 19^(th) depth maps and selects theweighted depth information of the objects A and B as the depthinformation of the objects A and B in the merged depth map.

Take the implementation for selecting the depth information of theobject in one of the depth maps which have the resolutions of the objectlarger than the threshold resolution as depth information of the objectin the merged depth map as the example. When the image capturing module21 have eight cameras, 28 (C₂ ⁸) images are generated accordingly.Assuming the object A appears in the fourth, fifth, and ninth depthmaps, the object B appears in the 14^(th), 15^(th), 19^(th), and 20^(th)depth maps, the resolutions of the object A in the fifth and ninth depthmaps are larger than the threshold resolution, and the resolutions ofthe object B in the 14^(th), 15^(th), 19^(th), and 20^(th) depth mapsare larger than the threshold resolution, the depth map merger 2213selects the depth information of the object A in one of the fifth andninth depth maps as the depth information of the object A in the mergeddepth map, and selects the depth information of the object B in one ofthe 14^(th), 15^(th), 19^(th), and 20^(th) depth maps as the depthinformation of the object B in the merged depth map.

Take the implementation for performing the weighting calculation on thedepth information of the object in the depth maps which have resolutionsof the object larger than the threshold resolutions and selecting theweighted depth information of the object as the depth information of theobject in the merged depth map as the example. When the image capturingmodule 21 have eight cameras, 28 (C₂ ⁸) images are generatedaccordingly. Assuming the object A appears in the fourth, fifth, andninth depth maps, the object B appears in the 14^(th), 15^(th), 19^(th),and 20^(th) depth maps, the resolutions of the object A in the fifth andninth depth maps are larger than the threshold resolution, and theresolutions of the object B in the 14^(th), 15^(th), 19^(th), and20^(th) depth maps are larger than the threshold resolution, the depthmap merger 2213 performs the weighting calculation on the depthinformation of the object A in the fifth and ninth depth maps, and onthe depth information of the object B in the 14^(th), 15^(th), 19^(th),and 20^(th) depth maps and selects the weighted depth information of theobjects A and B as the depth information of the objects A and B in themerged depth map.

One implementation of the focus distance calculating module 222 isillustrated as follows, but the present disclosure does not limit theimplementation of the focus distance calculating module 222. The focusdistance calculating module 222 comprises a focus distance calculator2221, wherein the focus distance calculator 2221 electrically connectedbetween the control interface 223 and the storage device 2210″.

The focus distance calculator 2221 obtains the merged map, and extractsthe depth information of the single one object or the multiple objects,and calculates the target focus distance of the object according to thedepth information of the object and transmits the target focus distanceof the object to the control interface 223. The control interface 223can allow the user to select one of the target focus distances of themultiple objects calculated by the focus distance calculator 2221, andthen transmits the selected target focus distance to the actuator module213. The actuator module 213 adjusts the actual focus distance of themulti-lenses module 211 according to the target focus distance of thesingle one object or the selected one of the multiple objects.

It can be known that, the automatic focusing device 22 in the exemplaryembodiment can finish focusing procedure in short time, even before theimage processing is finished. The automatic focusing device 22 can beimplemented by at least one of the software, hardware, and firmware. Forexample, the automatic focusing device 22 is implemented by theincorporation of the software and firmware, such the cameras of theimage capturing device 2 can perform automatic focusing withoutmodifying the hardware of circuits. Furthermore, since the imagecapturing device 2 has at least three cameras, the focusing accuracy canbe enhanced. Moreover, the actuator module 213 can be selectivelyimplemented by the closed-loop actuator module, so as to accurately setthe actual focus distance of the multi-lenses module 211 associated withthe cameras to be the received target focus distance.

[Exemplary Embodiment of Image Capturing Module]

One exemplary embodiment as follows is given to illustrateimplementation of the image capturing module 21, but the presentdisclosure does not limit the implementation of the image capturingmodule 21.

Referring to FIG. 2 and FIG. 3, FIG. 3 is a schematic diagram showing animage capturing module according to an exemplary embodiment of thepresent disclosure. The image capturing module 21 comprises amulti-lenses module 211, a multi-sensors module 212 and an actuatormodule 213. The multi-lenses module 211 comprises multiple lenses 2111arranged as an array, wherein the distance between the two lens modules2111 on the horizontal or vertical direction is L, and the distancebetween the two lens modules 2111 on the diagonal direction is √{squareroot over (2)}L. The multi-sensors module 212 has multiple sensing unitscorrespondingly disposed under the lens modules 2111, wherein eachlenses 2111 corresponds to one of the sensing units, such that thecameras can capture the scene to generate the images through the sensingunits and the lenses 2111. The actuator module 213 in the exemplaryembodiment can be a voice motor module, and the actuator 2132 can be avoice coil motor. The actuator driver 2131 drives the actuator 2132 tomove upward or downward, and thus the actual focus distance of themulti-lenses module 211 can be adjusted. In one other exemplaryembodiment, the actuator module 213 can be a shape memory alloysactuator module, and the actuator 2132 can be a shape memory alloysactuator. The image capturing module 21 may further comprise a flexiblebus 214 to electrically connect the image capturing module 21 and theautomatic focusing device 22. The image capturing module 21 can alsocomprise an optic image stabilizer (not shown in drawings) to make theimage capturing module 21 have the optic anti-shake function.

[Exemplary Embodiment of Automatic Focusing Method]

Referring to FIG. 4, FIG. 4 is a schematic diagram showing an automaticfocusing method according to an exemplary embodiment of the presentdisclosure. The automatic focusing method in FIG. 4 can be executed inthe image capturing device, such as the image capturing device 2 of FIG.2. At step S41, through multiple cameras of the image capturing device2, a scene is capture to obtain multiple images generated correspondingto the cameras, wherein the scene comprises a single one object ormultiple objects. At step S42, the automatic focusing device 22generates multiple depth maps according to the images, wherein eachdepth map is generated by the arbitrary two images. The depth map hasdepth information of the single one object or at least one of themultiple objects (if the two images which form the depth map have thesingle one object or at least the same one of multiple objects), or doesnot have the depth information of the single one object or all of themultiple objects (if the two images which form the depth map do not havethe single one object or at least the same one of multiple objects).

At step S43, according to resolutions of the single one or the multipleobjects in the depth maps, the automatic focusing device 22 selects thedepth information of the single one or the multiple objects in the depthmaps to generate a merged depth map. The details how the depthinformation of the single one or the multiple objects in the depth mapsis selected to generate a merged depth map according to the resolutionsof the single one or the multiple objects in the depth maps areillustrated above, thus omitting the redundant descriptions.

At step S44, according to the merged depth map, the automatic focusingdevice 22 calculates a target focus distance of the single one object ortarget focus distances of the multiple objects. At step S45, accordingto the target focus distance of the single one object or one of thetarget focus distances of the multiple objects, the actuator module 213adjusts an actual focus distance of the multi-lenses module associatedwith the cameras. Several usage scenarios are given to explain theexecution of the automatic focusing method in following descriptions,and the following usage scenarios do not limit the present disclosure.

[Schematic Usage Scenario Executing of Automatic Focusing Method forSchematic Usage Scenarios]

Referring to FIG. 5A, FIG. 5A is a schematic diagram showing the usagescenario of the automatic focusing method for an actual scene accordingto an exemplary embodiment of the present disclosure. In FIG. 5A, theimage capturing device has the cameras arranged as an 1×4 array, and thefour cameras respectively have the lenses 511 through 514, wherein theview angles of the lenses are presented as the slope lines, and fourobjects 521 through 524 appear in the scene of FIG. 5A.

Regarding the lens 511, the objects 521, 522 locate within the viewangle of the lens 511 (i.e. the objects 523 and 524 locate outside theview angle of the lens 511), and the image corresponding to the lens 511has the objects 521 and 522. Regarding the lens 512, the objects 521through 524 locate within the view angle of the lens 512, the imagecorresponding to the lens 512 has the objects 521 through 523 since theobject 523 shadows the object 524. Regarding the lens 513, though theobjects 521 through 524 locate within the view angle of the lens 513,the image corresponding to the lens 513 has the objects 521, 523, and524 since the object 523 shadows the object 522. Regarding the lens 514,the objects 521, 524 locate within the view angle of the lens 514 (i.e.the objects 522 and 523 locate outside the view angle of the lens 514),and the image corresponding to the lens 514 has the object 524 since theobject 524 shadows the object 521.

The automatic focusing method generate six (C₂ ⁴) depth maps accordingto the four images corresponding to the lenses 511 through 514. Theimages corresponding to the lenses 511 and 512 can be used to generate afirst depth map having the depth information of the objects 521 and 522.The images corresponding to the lenses 512 and 513 can be used togenerate a second depth map having the depth information of the objects521 and 523. The images corresponding to the lenses 513 and 514 can beused to generate a third depth map having the depth information of theobject 524. The images corresponding to the lenses 511 and 513 can beused to generate a fourth depth map having the depth information of theobject 521. The images corresponding to the lenses 512 and 514 can beused to generate a fifth depth map having no depth information of theobjects. The images corresponding to the lenses 511 and 514 can be usedto generate a sixth depth map having no depth information of theobjects.

In these six depth maps, the first, second, and fourth depth maps havethe depth information of the object 521. Since the resolution of theobject 521 in the fourth depth map is larger than the resolutions of theobject 521 in the first and second depth maps (the distance between thelenses 511 and 512 and the distance between the lenses 512 and 513 aresmaller than the distance between the lenses 511 and 513), thus thedepth information of the object 521 in the fourth depth map is selectedto the merged depth map. The objects 522, 523, and 524 merely appear inthe first, second, and third depth maps respectively, and thus the depthinformation of the object 522 in the first depth map, the depthinformation of the object 523 in the second depth map, and the depthinformation of the object 524 in the third depth map is selected to themerged depth map. Next, the automatic focusing method can calculate thetarget focus distance of the objects 521 through 524 according to thedepth information of the objects 521 through 524 in the merged depthmap. By using the control interface, the user can select one of thetarget focus distances of the objects 521 through 524 to adjust actualfocus distance of the multi-lenses module associated with the cameras(i.e. the actual focus distance of the lenses 511 through 514).

[Another Schematic Usage Scenario Executing of Automatic Focusing Methodfor Schematic Usage Scenarios]

Referring to FIG. 5B, FIG. 5B is a schematic diagram showing the usagescenario of the automatic focusing method for another actual sceneaccording to another exemplary embodiment of the present disclosure. InFIG. 5B, the image capturing device has the cameras arranged as an 1×4array, and the four cameras respectively have the lenses 511 through514, wherein the view angles of the lenses are presented as the slopelines, and four objects 521 through 524 appear in the scene of FIG. 5B.

Regarding the lens 511, the object 524 locates within the view angle ofthe lens 511 (i.e. the objects 521 through and 523 locate outside theview angle of the lens 511), and the image corresponding to the lens 511has the object 524. Regarding the lens 512, the objects 521 through 524locate within the view angle of the lens 512 and do not shadow eachother, and the image corresponding to the lens 512 has the objects 521through 524. Regarding the lens 513, though the objects 521 through 524locate within the view angle of the lens 513, the image corresponding tothe lens 513 has the objects 521, 523, and 524 since the object 521shadows the object 522. Regarding lens 514, the objects 521 and 522locate within the view angle of the lens 513 (i.e. the objects 523 and524 locate outside the lens 514), and the image corresponding to thelens 514 has the objects 521 and 522.

The automatic focusing method generate six (C₂ ⁴) depth maps accordingto the four images corresponding to the lenses 511 through 514. Theimages corresponding to the lenses 511 and 512 can be used to generate afirst depth map having the depth information of the object 524. Theimages corresponding to the lenses 512 and 513 can be used to generate asecond depth map having the depth information of the objects 521, 523,and 524. The images corresponding to the lenses 513 and 514 can be usedto generate a third depth map having the depth information of the object521. The images corresponding to the lenses 511 and 513 can be used togenerate a fourth depth map having the depth information of the object524. The images corresponding to the lenses 512 and 514 can be used togenerate a fifth depth map having the depth information of the objects521 and 522. The images corresponding to the lenses 511 and 514 can beused to generate a sixth depth map having no depth information of theobjects.

In these six depth maps, the second, third, and fifth depth maps havethe depth information of the object 521. Since the resolution of theobject 521 in the fifth depth map is larger than the resolutions of theobject 521 in the second and third depth maps (the distance between thelenses 512 and 513 and the distance between the lenses 513 and 514 aresmaller than the distance between the lenses 512 and 514), thus thedepth information of the object 521 in the fifth depth map is selectedto the merged depth map.

The objects 522 and 523 merely appear in the fifth and second depth mapsrespectively, and thus the depth information of the object 522 in thefifth depth map and the depth information of the object 523 in thesecond depth map are selected to the merged depth map. The first,second, and fourth depth maps have the depth information of the object524. Since the resolution of the object 524 in the fourth depth map islarger than the resolutions of the object 524 in the first and thirdsecond maps (the distance between the lenses 511 and 512 and thedistance between the lenses 512 and 513 are smaller than the distancebetween the lenses 511 and 513), thus the depth information of theobject 524 in the fourth depth map is selected to the merged depth map.Next, the automatic focusing method can calculate the target focusdistance of the objects 521 through 524 according to the depthinformation of the objects 521 through 524 in the merged depth map. Byusing the control interface, the user can select one of the target focusdistances of the objects 521 through 524 to adjust actual focus distanceof the multi-lenses module associated with the cameras (i.e. the actualfocus distance of the lens modules 511 through 514).

[Technical Results of Exemplary Embodiments]

To sum up, the exemplary embodiments of the present disclosure providean automatic focusing method, an automatic focusing device, and an imagecapturing device using the automatic focusing method. The automaticfocusing method captures a scene through the cameras of the imagecapturing device to obtain multiple images corresponding to the cameras,and generates multiple depth maps according to the images. The scene canhas single one object or multiple objects, and the depth map has depthinformation of the single one object or at least one of the multipleobjects (if the two images which form the depth map have the single oneobject or at least the same one of multiple objects), or does not havethe depth information of the single one object or all of the multipleobjects (if the two images which form the depth map do not have thesingle one object or at least the same one of multiple objects).According to the resolutions of the single one object or the multipleobjects in the depth maps, the automatic focusing method selects depthinformation of the single one object or the multiple objects in thedepth maps to generate a merged depth map. Then, the automatic focusingmethod calculates a target focus distance of the single one object ortarget focus distances of the multiple objects according to the mergeddepth map, and adjusts an actual focus distance of the multi-lensesmodule associated with the cameras according to the target focusdistance of the single one object or one of the target focus distancesof the multiple objects to finish automatic focusing.

It can be known that, the automatic focusing method and the automaticfocusing device using the automatic focusing method can fast finish thefocusing procedure and enhance the focusing accuracy. The automaticfocusing method and the automatic focusing device can find the focusdistance for a static image of the scene, and further for a dynamicvideo of the scene. The complexity for implementing the automaticfocusing method and the automatic focusing device is not high, and itcan be achieved by integrating a small chip in the existed imagecapturing device having the cameras. The automatic focusing method andthe automatic focusing device can further reduce the step movementnumber of the actuator for focusing and the accumulated movementdeviation. In short, the automatic focusing method and the automaticfocusing device can be implemented without high complexity, and have thefast focusing speed and accurate focusing ability.

The above-mentioned descriptions represent merely the exemplaryembodiment of the present disclosure, without any intention to limit thescope of the present disclosure thereto. Various equivalent changes,alternations or modifications based on the claims of present disclosureare all consequently viewed as being embraced by the scope of thepresent disclosure.

What is claimed is:
 1. An automatic focusing method, executed in animage capturing device, comprising: through multiple cameras of theimage capturing device, capturing a scene, so as to obtain multipleimages generated corresponding to the cameras, wherein the scenecomprises a single one object or multiple objects; generating multipledepth maps according to the images, wherein each of the depth map isgenerated according to the arbitrary two images, and the depth map hasdepth information of the single one object or at least one of themultiple objects, or does not have the depth information of the singleone object or all of the multiple objects; according to resolutions ofthe single one or the multiple objects in the depth maps, selecting thedepth information of the single one or the multiple objects in the depthmaps to generate a merged depth map; according to the merged depth map,calculating a target focus distance of the single one object or targetfocus distances of the multiple objects; and according to the targetfocus distance of the single one object or one of the target focusdistances of the multiple objects, adjusting an actual focus distance ofthe multi-lenses module associated with the cameras.
 2. The automaticfocusing method according to claim 1, wherein in the step “according tothe resolutions of the single one or the multiple objects in the depthmaps, selecting the depth information of the single one or the multipleobjects in the depth maps to generate a merged depth map”, for thesingle one object or each of the multiple objects, if the object appearsin portion or all of the depth maps, the depth information of the objectin the depth map which has a maximum resolution of the object isselected as depth information of the object in the merged depth map; forthe single one object or each of the multiple objects, if the objectmerely appears in one of the depth maps, the depth information of theobject in the depth map is selected as the depth information of theobject in the merged depth map.
 3. The automatic focusing methodaccording to claim 1, wherein in the step “according to the resolutionsof the single one or the multiple objects in the depth maps, selectingthe depth information of the single one or the multiple objects in thedepth maps to generate a merged depth map”, for the single one object oreach of the multiple objects, if the object appears in the portion orall of the depth maps, the resolutions of the object in the depth mapsare compared, and the depth information of the object in the depth mapwhich has a maximum resolution of the object is selected as depthinformation of object in the merged depth map; for the single one objector each of the multiple objects, if the object merely appears in one ofthe depth maps, the depth information of the object in the depth map isselected as the depth information of the object in the merged depth map.4. The automatic focusing method according to claim 1, wherein in thestep “according to the resolutions of the single one or the multipleobjects in the depth maps, selecting the depth information of the singleone or the multiple objects in the depth maps to generate a merged depthmap”, for the single one object or each of the multiple objects, if theobject appears in the portion or all of the depth maps, the depthinformation of the object in one of the depth maps which have theresolutions of the object larger than a threshold resolution is selectedas depth information of the object in the merged depth map; for thesingle one object or each of the multiple objects, if the object merelyappears in one of the depth maps, the depth information of the object inthe depth map is selected as the depth information of the object in themerged depth map.
 5. The automatic focusing method according to claim 1,wherein in the step “according to the resolutions of the single one orthe multiple objects in the depth maps, selecting the depth informationof the single one or the multiple objects in the depth maps to generatea merged depth map”, for the single one object or each of the multipleobjects, if the object appears in the portion or all of the depth maps,a weighting calculation is performed on the depth information of theobject in the depth maps which have the resolutions of the object largerthan a threshold resolution, and weighted depth information of theobject is selected as depth information of the object in the mergeddepth map; for the single one object or each of the multiple objects, ifthe object merely appears in one of the depth maps, the depthinformation of the object in the depth map is selected as the depthinformation of the object in the merged depth map.
 6. The automaticfocusing method according to claim 1, wherein in the step “according tothe resolutions of the single one or the multiple objects in the depthmaps, selecting the depth information of the single one or the multipleobjects in the depth maps to generate a merged depth map”, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, a weighting calculation isperformed on the depth information of the object in the depth maps whichhave resolutions of the object within top ranks, and weighted depthinformation of the object is selected as depth information of the objectin the merged depth map; for the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth information of the object in the depth map is selected as thedepth information of the object in the merged depth map.
 7. Theautomatic focusing method according to claim 1, wherein a number of thecameras is larger than or equal to
 3. 8. The automatic focusing methodaccording to claim 1, wherein the cameras are arranged as an N×M array,wherein N and M are integers larger than or equal to 1, but a product ofN and M are larger than or equal to
 3. 9. An automatic focusing device,adapted to an image capturing device, wherein multiple cameras of theimage capturing device capture a scene having single one object ormultiple objects, and the automatic focusing device comprises: a mergeddepth map generating module, for executing steps of: obtaining multipleimages generated corresponding to the cameras; generating multiple depthmaps according to the images, wherein each of the depth map is generatedaccording to the arbitrary two images, and the depth map has depthinformation of the single one object or at least one of the multipleobjects, or does not have the depth information of the single one objector all of the multiple objects; and according to resolutions of thesingle one or the multiple objects in the depth maps, selecting thedepth information of the single one or the multiple objects in the depthmaps to generate a merged depth map; and a focus distance calculatingmodule, electrically connected to the merged depth map generatingmodule, for executing a step of: according to the merged depth map,calculating a target focus distance of the single one object or targetfocus distances of the multiple objects, wherein the target focusdistance of the single one object or one of the target focus distancesof the multiple objects is used to adjust an actual focus distance ofthe multi-lenses module associated with the cameras.
 10. The automaticfocusing device according to claim 9, wherein in the step “according tothe resolutions of the single one or the multiple objects in the depthmaps, selecting the depth information of the single one or the multipleobjects in the depth maps to generate a merged depth map”, for thesingle one object or each of the multiple objects, if the object appearsin the portion or all of the depth maps, the depth information of theobject in the depth map which has a maximum resolution of the object isselected as depth information of the object in the merged depth map; forthe single one object or each of the multiple objects, if the objectmerely appears in one of the depth maps, the depth information of theobject in the depth map is selected as the depth information of theobject in the merged depth map.
 11. The automatic focusing deviceaccording to claim 9, wherein in the step “according to the resolutionsof the single one or the multiple objects in the depth maps, selectingthe depth information of the single one or the multiple objects in thedepth maps to generate a merged depth map”, for the single one object oreach of the multiple objects, if the object appears in the portion orall of the depth maps, the resolutions of the object in the depth mapsare compared, and the depth information of the object in the depth mapwhich has a maximum resolution of the object is selected as depthinformation of object in the merged depth map; for the single one objector each of the multiple objects, if the object merely appears in one ofthe depth maps, the depth information of the object in the depth map isselected as the depth information of the object in the merged depth map.12. The automatic focusing device according to claim 9, wherein in thestep “according to the resolutions of the single one or the multipleobjects in the depth maps, selecting the depth information of the singleone or the multiple objects in the depth maps to generate a merged depthmap”, for the single one object or each of the multiple objects, if theobject appears in the portion or all of the depth maps, the depthinformation of the object in one of the depth maps which have theresolutions of the object larger than a threshold resolution is selectedas depth information of the object in the merged depth map; for thesingle one object or each of the multiple objects, if the object merelyappears in one of the depth maps, the depth information of the object inthe depth map is selected as the depth information of the object in themerged depth map.
 13. The automatic focusing device according to claim9, wherein in the step “according to the resolutions of the single oneor the multiple objects in the depth maps, selecting the depthinformation of the single one or the multiple objects in the depth mapsto generate a merged depth map”, for the single one object or each ofthe multiple objects, if the object appears in the portion or all of thedepth maps, a weighting calculation is performed on the depthinformation of the object in the depth maps which have the resolutionsof the object larger than a threshold resolution, and weighted depthinformation of the object is selected as depth information of the objectin the merged depth map; for the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth information of the object in the depth map is selected as thedepth information of the object in the merged depth map.
 14. Theautomatic focusing device according to claim 9, wherein in the step“according to the resolutions of the single one or the multiple objectsin the depth maps, selecting the depth information of the single one orthe multiple objects in the depth maps to generate a merged depth map”,for the single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, a weighting calculationis performed on the depth information of the object in the depth mapswhich have resolutions of the object within top ranks, and weighteddepth information of the object is selected as depth information of theobject in the merged depth map; for the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth information of the object in the depth map is selected as thedepth information of the object in the merged depth map.
 15. Theautomatic focusing device according to claim 9, wherein a number of thecameras is larger than or equal to
 3. 16. The automatic focusing deviceaccording to claim 9, wherein the cameras are arranged as an N×M array,wherein N and M are integers larger than or equal to 1, but a product ofN and M are larger than or equal to
 3. 17. An image capturing device,comprising: an image capturing module, having multiple cameras, andcomprising a multi-lenses module, a multi-sensors module, and anactuator module; and an automatic focusing device, electricallyconnected to the image capturing module, comprising: a merged depth mapgenerating module, electrically connected to the image capturing module;and a focus distance calculating module, electrically connected to themerged depth map generating module and the image capturing module;wherein the image capturing module executes steps of: through thecameras, capturing a scene, so as to obtain multiple images generatedcorresponding to the cameras, wherein the scene comprises a single oneobject or multiple objects; and through the actuator module, accordingto a target focus distance of the single one object or one of targetfocus distances of the multiple objects, adjusting an actual focusdistance of the multi-lenses module associated with the cameras; whereinthe merged depth map generating module executes steps of: obtaining theimages corresponding to the cameras; generating multiple depth mapsaccording to the images, wherein each of the depth map is generatedaccording to the arbitrary two images, and the depth map has depthinformation of the single one object or at least one of the multipleobjects, or does not have the depth information of the single one objector all of the multiple objects; and according to resolutions of thesingle one or the multiple objects in the depth maps, selecting thedepth information of the single one or the multiple objects in the depthmaps to generate a merged depth map; wherein the focus distancecalculating module executes a step of: according to the merged depthmap, calculating the target focus distance of the single one object orthe target focus distances of the multiple objects.
 18. The imagecapturing device according to claim 17, wherein in the step “accordingto the resolutions of the single one or the multiple objects in thedepth maps, selecting the depth information of the single one or themultiple objects in the depth maps to generate a merged depth map”, forthe single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, the depth informationof the object in the depth map which has a maximum resolution of theobject is selected as depth information of the object in the mergeddepth map; for the single one object or each of the multiple objects, ifthe object merely appears in one of the depth maps, the depthinformation of the object in the depth map is selected as the depthinformation of the object in the merged depth map.
 19. The imagecapturing device according to claim 17, wherein in the step “accordingto the resolutions of the single one or the multiple objects in thedepth maps, selecting the depth information of the single one or themultiple objects in the depth maps to generate a merged depth map”, forthe single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, the resolutions of theobject in the depth maps are compared, and the depth information of theobject in the depth map which has a maximum resolution of the object isselected as depth information of object in the merged depth map; for thesingle one object or each of the multiple objects, if the object merelyappears in one of the depth maps, the depth information of the object inthe depth map is selected as the depth information of the object in themerged depth map.
 20. The image capturing device according to claim 17,wherein in the step “according to the resolutions of the single one orthe multiple objects in the depth maps, selecting the depth informationof the single one or the multiple objects in the depth maps to generatea merged depth map”, for the single one object or each of the multipleobjects, if the object appears in the portion or all of the depth maps,the depth information of the object in one of the depth maps which havethe resolutions of the object larger than a threshold resolution isselected as depth information of the object in the merged depth map; forthe single one object or each of the multiple objects, if the objectmerely appears in one of the depth maps, the depth information of theobject in the depth map is selected as the depth information of theobject in the merged depth map.
 21. The image capturing device accordingto claim 17, wherein in the step “according to the resolutions of thesingle one or the multiple objects in the depth maps, selecting thedepth information of the single one or the multiple objects in the depthmaps to generate a merged depth map”, for the single one object or eachof the multiple objects, if the object appears in the portion or all ofthe depth maps, a weighting calculation is performed on the depthinformation of the object in the depth maps which have the resolutionsof the object larger than a threshold resolution, and weighted depthinformation of the object is selected as depth information of the objectin the merged depth map; for the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth information of the object in the depth map is selected as thedepth information of the object in the merged depth map.
 22. The imagecapturing device according to claim 17, wherein in the step “accordingto the resolutions of the single one or the multiple objects in thedepth maps, selecting the depth information of the single one or themultiple objects in the depth maps to generate a merged depth map”, forthe single one object or each of the multiple objects, if the objectappears in the portion or all of the depth maps, a weighting calculationis performed on the depth information of the object in the depth mapswhich have resolutions of the object within top ranks, and weighteddepth information of the object is selected as depth information of theobject in the merged depth map; for the single one object or each of themultiple objects, if the object merely appears in one of the depth maps,the depth information of the object in the depth map is selected as thedepth information of the object in the merged depth map.
 23. The imagecapturing device according to claim 17, wherein a number of the camerasis larger than or equal to
 3. 24. The image capturing device accordingto claim 17, wherein the cameras are arranged as an N×M array, wherein Nand M are integers larger than or equal to 1, but a product of N and Mare larger than or equal to 3.